Tarnost does not appear in the close-up map of Gondor in The Return of the King.[1] The first reference is in The War of the Ring: In the Western map section there is a dot visible in square Q12 at the northern tip of the hills south of the Ringló, and the text states that it had a penciled note calling it Tarnost.[2] The second reference appears in Sauron Defeated: In a manuscript Tolkien stated that "From Erech a road ran by [the] sea, skirting in a loop the hills of Tarnost, and so to Ethir Anduin and the Lebennin.".[3]

Hammond and Scull suggest that Tarnost appears to be an earlier name for Ethring, as they share a "similar position on the published map".[4]